In recent years, magneto-optical recording/reproducing apparatuses have become compact with higher performance, in which reading and reproducing are performed by optical pickups on optical discs acting as recording mediums. Portable MD recorders using MiniDisc (MD) have become generally available as such portable magneto-optical recording/reproducing apparatuses with smaller size and higher performance.
A conventional magneto-optical recording/reproducing apparatus is disclosed in, for example, Japanese Patent Laid-Open No. 2002-32938. Referring to FIGS. 35 to 42, the magneto-optical recording/reproducing apparatus will be discussed below.
As shown in FIG. 35, in the magneto-optical recording/reproducing apparatus, an electric circuit 102 and a mechanical mechanism 103 are stored in a body cabinet 101. The magneto-optical recording/reproducing apparatus has a lid 104 covering the opening of the body cabinet 101. The mechanical mechanism 103 comprises a mechanical base 105 and a mechanical part 106 placed on the mechanical base 105. A mini disc 107 loaded in a storage space between the mechanical base 105 and the mechanical part 106 has an optical disc 109, on which signals such as a music signal can be recorded and reproduced, in a cartridge 108. The optical disc 109 is a known disc such as a magneto-optical disc.
Referring to FIG. 36, the following will discuss various components placed on a holder 110 of the mechanical part 106. A lifter 111 has a hinge shaft 112 which is engaged with a hinge bearing 113 formed on the holder 110, so that the lifter 111 swings up and down. A drive rod 114 is slidably placed on the holder 110. A wedge 115 of the drive rod 114 is engaged with and removed from a wedge receiving portion 116 formed on the lifter 111.
A driving gear 118 is placed on a motor 117 screwed onto the holder 110, and a reduction gear 119 engaged with the driving gear 118 is rotatably placed on the holder 110 via a shaft 120. A transmission gear unit 122 is placed between the reduction gear 119 and an SW piece 121 provided on the drive rod 114. The transmission gear unit 122 is made up of a worm wheel 124 and a feed gear 125 which are rotated together via a shaft 123. As shown in FIG. 37, a worm 126 is integrally placed on the reduction gear 119. The worm 126 is engaged with the worm wheel 124 and the feed gear 125 is engaged with an engaging claw 127 of the SW piece 121.
A magnetic head unit 128 has a magnetic head 129 which can swing up and down. The base end of the magnetic head unit 128 is screwed onto a head angle 130, the head angle 130 is screwed onto a base 131, and the base 131 is placed on the mechanical base 105. As shown in FIG. 38A, when the lifter 111 swings to a lower position and does not support the magnetic head 129, the magnetic head 129 comes into a recording state where the magnetic head 129 is in sliding contact with the optical disc 109. When the lifter 111 swings to an upper position and lifts the magnetic head 129, as shown in FIG. 38B, the magnetic head 129 comes into a reproduction state where the magnetic head 129 is separated from the optical disc 109. As shown in FIG. 39, a spindle motor 132 for rotating the optical disc 109 is provided on the mechanical base 105.
In this configuration, the driving gear 118 is rotated by the driving of the motor 117, the reduction gear 119 engaged with the driving gear 118 is rotated with the worm 126 by the rotation of the driving gear 118, and the worm wheel 124 engaged with the worm 126 is rotated with the feed gear 125 via the shaft 123 by the rotation of the worm 126.
The SW piece 121 engaged with the feed gear 125 via the engaging claw 127 is moved with the drive rod 114 in the axial direction of the shaft 123 by the rotation of the feed gear 125. The moving direction of the drive rod 114 is determined by the rotation direction of the motor 117. The drive rod 114 is moved forward and backward in response to the normal and reverse rotations of the motor 117.
For example, FIGS. 40A and 40B show the reproduction state. As shown in FIG. 40A, the wedge 115 of the drive rod 114 presses up the wedge receiving portion 116 of the lifter 111 and keeps the lifter 111 at the upper position. Since the lifter 111 lifts the magnetic head 129, the magnetic head 129 is separated from the optical disc 109.
In this state, as shown in FIG. 40B, when the driving gear 118 is rotated counterclockwise by the driving of the motor 117, the feed gear 125 rotates via the reduction gear 119, the worm 126, the worm wheel 124, and the shaft 123, and as shown in FIG. 41B, the engaging claw 127 is moved to the right of FIG. 40B together with the SW piece 121 and the drive rod 114 by the rotation of the feed gear 125. With this configuration, as shown in FIG. 41A, the wedge 115 is moved in a direction separating from the wedge receiving portion 116 of the lifter 111. The magnetic head 129 moves close to the optical disc 109 as the lifter 111 swings to the lower position.
When the engaging claw 127 reaches one end of the feed gear 125 as shown in FIG. 42B, the wedge 115 moving with the SW piece 121 and the drive rod 114 reaches a position where the wedge receiving portion 116 of the lifter 111 is not pressed as shown in FIG. 42A. The lifter 111 is placed on the lower position and the magnetic head 129 is brought into sliding contact with the optical disc 109.
As described above, in the conventional magneto-optical recording/reproducing apparatus, the motor 117 is mounted on the holder 110 as shown in FIG. 37 as a mechanism for driving the lifter 111, and the turning force of the motor 117 is transmitted through the driving gear 118, the reduction gear 119, the worm 126, the worm wheel 124, and the feed gear 125. Thus, the upper part of the holder 110 requires a relatively large height to place these components.
This height is determined by one of a value obtained by adding the thickness of the body of the motor 117 and the thickness of the driving gear 118, a value obtained by adding the thickness of the body of the motor 117, the thickness of the reduction gear 119, and the height of a gap between the motor 117 and the reduction gear 119, and a value obtained by adding the diameter of the worm wheel 124, the thickness of the reduction gear 118, and the height of a gap between the worm wheel 124 and the reduction gear 118. Since it is difficult to reduce this height, a portable MD recorder has a large thickness.
Further, the structure becomes large because of the complicated reduction mechanism in which the turning force of the motor 117 is reduced by two or more gears and then transmitted. Moreover, the motor is expensive. For this reason, the number of components increases and the manufacturing cost rises. The control of an electric signal also tends to become complicated in order to improve trackability for the electric signal.
Similar problems rise even if a plunger is used instead of the motor 117. The size of the mechanism is determined by the size of the plunger and the plunger causes high cost.